Mette Bryndum, the Windmill Team

Why and how we built Tvindkraft

During Christmas in 1974 Tvind’s teacher group decided to build the windmill. It was a practical decision: We had experienced the oil crisis in ’73, where the price of 1 liter of oil went up from 3 to almost 12 dollars.

The Government’s plan was to introduce nuclear power in Denmark. Five sites had been located in Denmark for nuclear power plants.

To us it was clear that what Denmark needed was Renewable Energy. We did not think that yet another problematic type of energy supply was needed, especially not a technical solution where the problem of waste was unsolved – waste which would pose a question for future generations for thousands of years.

The AddTvind’s Teacher Group placed an add in the papers:

”Windmill builders wanted -Who would like to participate in building a 54 meter tall wind turbine at the Tvind Schools? Skilled as well as unskilled windmill builders wanted for immediate start. The process is expected to last five months.”

The Windmill Team was composed of many different people. For example there were teachers, farmers, plumbers, Folk High School Students, artists, carpenters, chemists, unemployed people, poets, engineers and many others. Our average age was 21. About half the team were girls.I myself was 15, straight out of grade 9. I started in the wing team, the wing root to be specific, together with for example Joep – a Dutch artist - and Janne. The windmill team displayed great variety.But – one thing we had in common: None of us knew how to build a windmill.

We decided:What we did not comprehend – we had to make comprehensibleWhat we did not know – we had to exploreWhat we couldn’t do – we had to learn

We were the ones who had the responsibility, and we had to understand why everything was made the way it was. We had to understand which reservations the calculations held and why.We had to understand which forces we were calculating with and why.Each and every detail had to be thought through. It soon appeared to be a wise strategy.

The ready-mixed concrete for the foundation turned out to be so expensive that it would undermine the budget totally. The only way out was to buy a huge, second-hand concrete mixer, close to a concrete factory, mixing the concrete ourselves.When mixing the concrete, 1 liter of water too much was enough to ruin 1.5 cubic metres of concrete. Therefore we appointed three persons to get a “concrete mixer license”.

Issuing driving licenses was something we introduced for all mechanical and dangerous work. We studied and passed an exam. At the exam you showed that you understood all safety and quality demands. Then you got your “license”.I myself got a license for the small ”sausage machine”, and I still remember how proud I was when I got the license for mixing araldite.

Relying on our own forces was practised in matters big and small. The relying-on-own forces policy pervaded the technical solutions, f. inst. when the wings were designed: In a building meeting with the whole windmill team present, the engineer whom we had hired was asked to explain why he had chosen his particular design. The windmill team was not satisfied with his explanation.We decided to find a person who could give us advice. We found Ulrich Hütter in Stuttgart, a German professor of aero-dynamics, who had constructed the biggest large modern windmill: A 100 kWh windmill with 17.5 meter long blades. He confirmed our suspicion that the drawings that had been presented to us were far from satisfying.

Another example of the problem-solving capacity of the rely-on-one’s-own-forces policy was about the tower.The tower was going to be poured in a slip form, which was to move upwards continuously for three weeks without pause during the pouring of the tower. In preparation we built a small-scale model of clay in the precise proportions. When we were going to place the steel in our small model, there was no space for all the steel that was supposed to go into the concrete. There was spare steel. And absolutely no space in the concrete.Then we started checking the calculations and errors appeared.

Also I shall never forget the time when we had finished the first wing. Our fibre glass depot was curiously empty. We counted the rolls of fibre glass and found the our “fat” wing root – the wing root where I worked, as I said – this wing root was a very thick pipe – and this thick pipe was not including in neither use of materials nor weight. This meant that the first wing weighed 3.3 tons more than calculated and that there was hardly any fibre glass left.We solved it – but we were sweating ….The policy of relying-on-one’s-own-forces and our unity was of decisive importance for the result.

Inspiration and grass root movementWhen we started building the windmill in May of 1975, we did not tell much about it to the media. We figured it was better for the public to discover it bit by bit as the build progressed. This was precisely what happened.The first article appeared in one of the local papers in June ‘75. When we had completed the foundation, news about the windmill had appeared in all the big, national papers.

We started getting a lot of guests. We parked two busses next to the building site – guest busses – where we served tea for the guests.The busses soon became a centre for all kinds of discussions. We had one or two people from the windmill team in charge of the guest bus. Soon three people were needed in the guest bus and at that point we started ”borrowing” people from other teams in Tvind to take care of the bus.

Starting this huge windmill build touched something in people. People wanted us to be successful.People were also willing to contribute with help, with ideas, with cheap solutions. Sometimes with presents.

In the guest bus big as well as small questions were discussed. To one recurring question: “Why do you only want to make hot water?” ”Why not electricity?” our answer was that we could not control the revolutions of the windmill.One day a guest appeared who said, ”Why don’t you make a frequency converter? I can design one for you and my students can build it for you.” It was a professor from Danmarks Tekniske Universitet (The Technical University of Denmark – today DTU). His name was Ulrik Krabbe. Ulrik Krabbe also helped us find a very cheap gearbox and a generator. That was lucky…But it was not just luck: Along with the large numbers of people visiting us, good ideas floated in our direction. People with knowledge and ideas were attracted to our building site – like bees to honey. We were visionary and we showed a glimpse of a possible future, and most people who are faced with a good vision of the future, want to help turning it into reality.

People also came looking for our advice for projects they themselves wanted to launch.At one point we realized that we had to do more for people seeking our advice. Therefore we opened an energy office, ”West Jutland Energy Office”, where people could get designs and advice about renewable energy.At the end of the build we had close to 3.000 guests a day.

Finishing the buildAs I mentioned before, we had calculated on the build lasting for 5 months. It ended up taking years. The project changed along the road. Much was re-thought and re-designed, in particular did the new concept of producing electricity rather that hot water demand much more complicated constructions. The price also went up. When we started, the budget was 850.000 DKK. The final price of the windmill was around 6.5 million.During the build we applied for assistance to finance the project from all kinds of foundations, but no funds were forthcoming. Again the relying-on-one’s-own-forces policy was of decisive importance. In the end it was Tvind’s Teacher Group who earned all the money and paid for the whole build.

Determination and focusDuring the whole build one attitude was all pervasive:We were 100 % convinced that we wanted to and were able to finish the building of the windmill. No matter what difficulties we might run into on our way, we would conquer them. I don’t recall any sense of doubt – at any time. Of course we would succeed.

FinallyThere are so many stories that we have no time for sharing here – but you are welcome to ask us:About how we invented parachutes in the wing tips as a safety systemAbout how we got the wings in place About how we carried one wing out and back in and out again About how we learnt how to work with steel And much more

And today, 40 years after cutting the first sod, the windmill has spun numerous strands of good energy:In our hearts In our courage to take on new and different challengesIn our unityAnd as an important educational example for the next generation.